Edited AVI results in garbled video

[forumulhyde]

I have this 726mb anime which is too big to overburn on my CD burner, so I decided to cut it down. I didn't rip it myself, but the people I got it from added a promotional segment at the beginning that is as ostentatious as it is unnecessary. It amounts to 1% of the AVI - in this case, about 2000 frames - and I need to get rid of it.

So I load it up in VirtualDub, and cut it off, using the standard procedure found in the guide at this site. The resulting 718mb file is now of a size I can overburn. Unfortunately the video is now a psychadelic haze of inscrutable blocky color. The audio, on the other hand, appears to be unaffected.

What the h*** is going on here? How could cutting a part of the file off, and doing a direct stream copy, affect the video? I tried DivFix on the new file, but that didn't change anything. What's causing this, and what can I do about it?

Thanks for any light you can shed.

[The VidKid]

Unfortunately the video is now a psychadelic haze of inscrutable blocky color. The audio, on the other hand, appears to be unaffected.
What the h*** is going on here? How could cutting a part of the file off, and doing a direct stream copy, affect the video?
What's causing this, and what can I do about it?

Thanks for any light you can shed.

Wow, that's really strange. DIRECT STREAM COPY and the video is changed?? Hhm.. What version of of VDub are you using? Have you tried re-downloading a new, fresh copy in case it was a bad copy? That's really weird. Are you doing anything else to the video? Adding any filters? Or are you SIMPLY just doing a cut and save, and that's it?

[forumulhyde]

I'm using VirtualDub 1.4.8. The copy is fine - I can perform the same operation on other sources without a hitch, and have been, so it would not seem to be that (straight off.) But I downloaded the latest version anyway, "1.4.10" (hehe, umm, it used to be that 1.4.91 or 1.5 followed 1.4.9), and got the same result. I've also since tried saving in "old format AVI", grabbing at straws, but no difference.

No, I'm not doing anything else to the video; no filters, nothing. So unless something is on by default that shouldn't be for this source, then that's not it either.

As I've been experimenting, the only thing I've noticed so far that's different about it is that DivX Codec 4.11 was used (AVI Information > Decompressor.)

I know I have 3.11 and 4.12 installed, but if it wasn't apparent by now, I'm still a novice at working with these files and don't know if 4.12 is backward compatible to 4.11, etc.

So if anyone has any suggestions, or if you need more info before you can say, let me know. Until then, more research and experimentation - hopefully someone can beat me to it though

[The VidKid]

Hhm...
What kind of "blocky colour" does it produce?
Is it throughout the entire video?
Is there a way you can provide a clipped example via a link to take a look at? Or maybe a screen shot / single frame export?

DivX 4.12 is able to play 4.11, otherwise you wouldn't be able to see any video at all. But that wouldn't really matter since you're NOT compressing the video in 4.12, you're doing a DIRECT STREAM COPY.

Have you tried opening the video in different players? Windows Media Player 7.0, Media Player, DivX PLayer 2.0, etc..??

Try doing a Direct Stream Copy before cutting off the intro, and see if it's the cutting that's causing the problem. If not, then it's simply the DSC.
How about actually recompressing the video in DivX4.12 and seeing if that still causes the blockiness? Are you setting the priority to the HIGHEST?

[forumulhyde]

I might be able to provide a sample, but I don't know if it would help; suffice it to say that it is just garbage - visually that is, the audio is unaffected ofcourse. And yes, throughout the entire video.

I tried a DSC without any cuts, like you said, and the copy is fine. I also tried splitting it in half - resigning myself to using 2 CD's, but only the first half turned out normal. It's like there's something at the beginning of the file that has to be there for the rest of the file to be viewable, and any part that doesn't include it becomes "decrypted". And I choose that word because it's got me paranoid now - thinking that there's something in the promo clip in the beginning that makes the rest of the video unviewable if you try to cut it off. (So they can prevent anyone else from taking credit for their rip, and all the pathetically empty glory that goes with it.) Is that possible? To putting something in the header that every keyframe requires to...? Blah blah blah, I don't know. All I know is that I have a file I can't burn to CD.

[forumulhyde]

Well VirtualDub's author had the solution, which I include below in case anyone else runs in to this problem. Actually it's rather simple, and I have to kick myself for not having tried it.

"Try leaving in the first frame when you cut for the second segment.
Some versions of DivX 4 made the improper assumption that the first
keyframe of a compressed sequence would always be decompressed first,
which is not always true."

I just did a variation on this which was to delete the section I wanted out at the beginning of the file, leaving the first frame in. I did a DSC on the remainder, and the saved result played just fine.